Carburetor



July 7, 1964 1J. H. KREIN ETAL 3,139,874

CARBURETOR Y Filed May 1e, 196s INVENTORS JOHN H. KREIN United StatesPatent O M 3,139,874 CAREURETR John H. Krein, Florissant, and Forrest W.Cook, Webster Groves, Mo., assignors to ACF Industries, Incorporated,New Yorh, NX., a corporation of New Jersey Filed May 16, 1963, Sei'. No.289,900 13 Claims. (Cl. 12S-122) This invention relates to carburetorsand in particular to means to spoil or otherwise render inoperative theidle system in a carburetor when dangerous conditions are present.

A carburetor for an internal combustion engine, in accordance with thenature of this invention, includes a high speed fuel supply system andan idle fuel supply system. The high speed system has a fuel nozzlewhich supplies the mixture conduit with fuel near the top portion of thecarburetor. The throttle of the carburetor is normally located at alower portion of the carburetor. The idle fuel supply system is soarranged that it has a mixture Outlet port downstream of the throttleand an air inlet port adjacent the throttle plate in the curb idleposition thereof.

A reduction in engine compartment height as a result of modernautomative design necessitates in lower and more compact carburetordesign. Such compact carburetor design requires placement of thethrottle valve and throttle shaft in close proximity to the lowerportion of the throttle body. A carburetor of the type described will bemounted on the intake manifold of an internal combustion engine in sucha manner that hot exhaust gases from the exhaust system will Contact acertain specific area at the bottom of the carburetor, when the engineis cold, for the purpose of warming the carburetor for prevention of iceformation at the throttle plate. When normal temperatures areapproached, the hot exhaust gases actuate a thermostat in the exhaustsystem to substantially close a valve reducing the flow of eX- haustgases to the carburetor. Due to the tolerances of the thermostaticallyactuated valve, flow of exhaust gases through the carburetor warmingcircuit is severely reduced but not completely cut E.

A thin non-corrosive, heat-conductive shim is normally located at thelower portion of the Vthrottle body and separates the throttle body fromthe warming circuit thereby preventing direct contact of the hot exhaustgases on the valve body and eliminating the problem of corrosion due tothe action of the exhaust gases on the exposed carburetor portion.Exhaust gases contain acids which react with aluminum alloys from whichthe carburetor bodies are cast causing severe deterioration thereof.

When a carburetor formed of aluminum alloy is assembled to the manifoldof an internal combustion engine, without the shim, a very dangerouscondition exists. The exhaust gases will react with the exposed part ofthe carburetor body causing corrosion and deterioration of the throttleshaft and shaft bearings, thus causing the throttle to lock in an openposition against all forces tending to close it.

Accordingly, among the several objects of this invention may be notedthe prevention of throttle locking due to seizure of the throttle shaftresulting from exhaust gas corrosion.

It is an object of this invention to provide a carburetor, the idlesystem of which is reduced to an inoperative condition if the corrosionpreventing shim is not present.

Another object of this invention is to provide a carburetor having anidle system the adjustment of which, to achieve operation, is impossiblewhen the shim is not present.

It is amongthe objects of this invention to provide a carburetor whichnot only includes a spoilable idle sys- 3,139,874 Patented July 7, 1964ICC tem but also which is inexpensive in manufacture and reliable inuse.

Other objects and features will be in part apparent and in part printedout hereinafter.

The invention accordingly comprises the constructions hereinafterdescribed, the scope of the invention being indicated in the followingclaims.

In the accompanying drawings in which one of various possibleembodiments of the invention is illustrated,

FIGURE l is a view in side elevation of the engine of an automotivevehicle equipped with a carburetor, in accordance with this invention.

FIGURE 2 is a detail view in elevation with parts broken away, shown insection of a carburetor mounted on an engine, with air filter removedand provided in accordance with this invention with means for spoilingthe idle system.

FIGURE 3 is an enlarged partial view in elevation with parts broken awayin section of a throttle body, insulator and exhaust gas passagesprovided in accordance with this invention.

FIGURE 4 is a bottom view of the insulator spacer member taken alongline 4-*4 in FIGURE 2.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

Referring to the drawings, there is indicated at 1 in FIGURE 1 theinternal combustion engine of an automotive vehicle E. At 3 is indicatedthe carburetor for the engine and at 5 is vindicated the air filter onthe air horn of the carburetor. An exhaust manifold is indicated at 7,an intake manifold is indicated at 8 and a thermostatically controlledheat riser is shown at 9. Heat riser 9 includes a thermostaticallycontrolled valve 10 for controlling the flow of gases through thewarming circuit shown by arrows in FIGURE 2.

Referring now to FIGURE 2, the carburetor 3 is shown to comprise a mainbody casting formed with a vertical mixture conduit 25, a fuel bowl 27and an integral throttle section 33 having a throttle bore 35 coaxialwith and in continuation of the mixture conduit 25. The throttle sectionis xed to the inlet manifold 8 of engine 1.

An air horn casting includes a bowl cover 29 closing the fuel bowl 27.Extending across the airhorn 31 is a choke valve shaft 41 carrying achoke valve 43. A Choke control is generally indicated at 45.

A float valve 36 operated by a float 34 controls flow of fuel to thefuel bowl 27 from a fuel inlet 3S which is in turn connected to a fuelreservoir 40 by a fuel conduit 42, both schematically shown in FIGURE 2.

A throttle shaft 37 extends across the throttle bore and carriesthrottle valve 39. Throttle valve 39 is constituted by a plate fittingthe bore 35.

A boost venturi 47 is provided in the mixture conduit. A high speed fuelsystem for the carburetor comprises a metering jet S1 through which fuelmay ilow from the fuel bowl under control of shaped metering rod 53 to apassage 55 for delivery through a fuel nozzle 57 into the boost venturi47.

An idle fuel and air system is provided in the carburetor to supply afuel and air mixture yto the engine for low speed or idle operation. Theidle system comprises a fuel well 58 opening at its lower end into themain fuel passage 55. An idle fuel tube 59 having an open lower endextending below the normal fuel levelin well 58V is connected at itsupper end to a fuel passage 60 formed in the carburetor body. An airbleed 66 bleeds air into passage 60 changing the fuel into a richmixture. Passage 60 extends from the Well 58 lthrough the fuel bowl 27downwardly to an idle fuel chamber 61 formed in the throttle body 33.

An elongated idle port 62 opens chamber 61' into the throttle bore 35adjacent to the edge of the throttle valve 39 when in its curb idleposition. Passage 60 extends through chamber 61 into a bore 64 connectedby a second idle port 63 to the throttle bore downstream of the throttlevalve 39. An idle adjustment screw 65 is threaded into bore 64 and hasan inner pointed end to control iiow of the mixture through ports 62 and63.

A more detailed description of a carburetor of the type described hereinis found in Patent No. 2,635,625.

The elongated idle port 62 is only partially closed by the edge of thethrottle valve 39, when the valve is in its curb idle position and aportion of port 62 extends upstream of throttle 39, as shown in FIGURE2. This provides another air bleed into idle chamber 61 causing afurther break-up of the rich mixture resulting in a correct idlemixture. During engine idle or low speed operation, the negativepressure or vacuum in manifold M is in the order of 18 inches ofmercury. This vacuum is effective to draw through port 63 sufficientfuel from passage 60 and air through port 62 and additional air aroundthrottle valve 39 to operate the engine at low speeds with little or noload.

The intake manifold 8 has an exhaust gas passage 70 formed thereinforming a portion of the warming circuit, to be described. The exhaustgas inlet passage communicates with the exhaust manifold 7 through aheat riser passage 69.

An insulator spacer member 75 is located between the throttle section 33and the intake manifold and serves to insulate the throttle section 33from the engine heat during normal engine operation. The insulatormember 75 has an arcuate opening 76 therein forming a portion of theexhaust gas conducting circuit and allowing hot exhaust gases to impingedirectly upon the lower surface of the throttle section 33 to apply heatto the lower portion of the carburetor body and thereby prevent iceformation at the throttle plate. The upper wall 71 of the exhaust gasinlet passage 70 has an inlet opening 72 therein communicating theexhaust gas passage with the arcuate channel 76 in spacer 75 and anoutlet opening 71 communicating the arcuate channel 76 with an exhaustgas outlet 79. Hot exhaust gases flow upwardly into inlet passage 7 0,through opening 72 into arcuate chamber 76 and downwardly throughopening 71 through outlet passage 79 to the exhaust system.

The exhaust manifold 7 includes a valve 10 which is normally in ablocking position at low temperatures, as shown in FIGURE 2, and isautomatically moved to an unblocking position by a thermostatic coil 11,at a predetermined higher temperature to reduce the ow of hot exhaustgases to the carburetor through the riser passage 69 when the enginetemperature approaches the normal operating range. The unblockingposition of valve 10 is indicated by dotted lines in FIGURE 2.

A thin non-corrosive, heat-conductive shim 77 is located between theinsulator 75 and the throttle section 33. The purpose of the shim is toprotect the lower surface of the aluminum alloy carburetor from directcontact by the exhaust gases to prevent corrosion thereof. Strong acidspresent in exhaust gases react with the aluminum alloy and cause verysevere deterioration and failure of the carburetor wall structure.Corrosion of .the throttle shaft and throttle shaft bearings causes thethrottle to lock causing a very dangerous condition. The shim preventsthe exhaust gases from contacting the aluminum alloy and Valso transmitsheat to the throttle section of the carburetor.

CII

When the shim is present and the thermostatically controlled valve lilin the exhaust manifold is in its blocking position, hot engine exhaustgases will flow up the heat riser passage 69 through the arcuate opening76 to the shim 77 to heat an arcuate portion of the throttle section 33,as described. When the thermostatically controlled valve 10 moves to anunblocking position due to an increase in temperature, a lesser quantityof exhaust gases will flow up the riser passage 69 and the insulator 75will serve to limit the transfer of heat from the manifold to thecarburetor.

When the shim is not present, for example, due to failure of theserviceman to insert it when connecting the carburetor to the engine, inaccordance with the invention, exhaust gases under pressure will flowinto the idle chamber 61 through the idle spoiler passage 78. When theidle fuel chamber is subjected to pressure from the exhaust system, anumber of conditions exist in the idle system making adjustment thereofimpossible. The exhaust gases contain very little oxygen and reduce thefuel/ oxygen ratio of the idle mixture to a point where combustion inthe engine will no longer be supported. More important, pressure in theidle fuel chamber breaks or prevents the vacuum required to draw fuelfrom the fuel bowl thus shutting off the How of fuel through the idlesystem.

Since the shim 77 must be in place for the carburetor to functionnormally, there will be no possibility of a throttle shaft becomingseized due to corrosive action of the exhaust gases.

In carburetors having several bores, one or more idle spoiler bores willbe provided for each idle circuit.

It should be particularly noted that the spoiler bores are provided tospoil only the idle system of the carburetor and the engine willfunction as long as the high speed circuit or circuits are open, but assoon as the engine is reduced to idle, it will cease to operate. Normalstarting of an engine with the throttle at its curb idle position would,of course, be impossible without the presence of the shim.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes and modifications could be made in the aboveconstruction without departing from the scope of the invention, it isintended that all matter contained in the above description or shown inthe accompanying drawings shall be interpreted as illustrative and notin a limiting sense.

We claim:

1. In a combination, an internal combustion engine having an intakemanifold and an exhaust system, a carburetor mounted on said intakemanifold, said intake manifold having an exhaust gas passage adjacent toa portion of said carburetor and connected to said exhaust system toconvey hot exhaust gases to said carburetor portion, said carburetorhaving an idle system connected to said intake manifold, a thincorrosion resistant heat conductive shim located between said carburetorportion and said intake manifold and exposed to said exhaust gas passageto protect said carburetor from damage by exhaust gas corrosion, meansfor spoiling said idle system to prevent said engine at idle fromoperating at low speeds if said shim is not located between thecarburetor and the intake manifold.

2. The combination as set forth in claim l, wherein said means forspoiling said idle system comprises at least one conduit communicatingsaid exhaust system with said idle system only when said shim is notpresent.

3. The combination as set forth in claim l, wherein said means forspoiling said idle system comprises a passage in said carburetor betweensaid idle system and said exhaust gas passage, said shim forming aclosure for said passage.

4. An internal combustion engine comprising an intake manifold, anexhaust system, said intake manifold having a chamber therein connectedto said exhaust system, said chamber having an opening in the manifoldwall, a carburetor including a body mounted on said intake manifold,said body including a fuel bowl and a high speed fuel supply systemcommunicating with said fuel bowl, an idle system communicating withsaid fuel bowl and comprising a low speed metering jet located in saidbody, said body having a low speed fuel supply chamber communicatingwith said low speed metering jet, said carburetor mounted on said intakemanifold with a portion of the lower surface of said body incommunication with said intake manifold exhaust chamber whereby hotexhaust gases will contact said portion of said lower body surface andheat said carburetor, a thin corrosive resistant heat conductive shimlocated between said body surface and said intake manifold to protectsaid body surface from corrosion by the exhaust gases and to conductheat to said body surface, means for rendering said idle systeminoperative should said shim not be located between the body surface andintake manifold.

5. An internal combustion engine as set forth in claim 4, said means forrendering said idle system inoperative comprising conduit meanscommunicating said idle system with said exhaust system, said conduitmeans being closed by said shim.

6. A carburetor as set forth in claim 5, said bore means being formed insaid throttle portion and extending from said low speed fuel supplychamber to the lower surface of said throttle portion, said shimnormally closing said bore at the lower surface of said throttleportion.

7. In a carburetor for an internal combustion engine having a main bodyincluding a throttle portion, said main body and said throttle portionhaving an idle system therein, the throttle portion having a throttlebore therein, a throttle shaft mounted transversely of said throttlebore and adjacent the lower portion of said throttle portion, acorrosion resistant heat conductive shim located adjacent the lowerportion of said throttle portion in sealing engagement therewith toprotect said throttle portion against the corrosive action of exhaustgases, said carburetor being adapted for mounting on an intake manifoldhaving an exhaust gas passage therein directing exhaust gases to theshim, the exhaust gases impinging on said shim to heat said throttleportion, the improvement comprising means for spoiling the operation ofsaid idle system when said shim is not positioned between said throttleportion and said manifold.

8. A carburetor, as recited in claim 7, said spoiling means comprising abore in said throttle portion from said idle system to the lower surfaceof said throttle portion, said shim normally closing said bore at saidsurface whereby, exhaust gases under pressure will flow from saidexhaust gas passage into said idle system spoiling said idle system andrendering the engine inoperative at idle when said shim is not locatedbetween said throttle portion and said intake manifold.

9. A carburetor for an internal combustion engine having an opening inan outer wall thereof and a conduit for conducting exhaust gases to saidopening, said carburetor comprising a body having a mixture conduittherethrough, means at one end of said mixture conduit for mounting saidcarburetor body with a portion of said body superimposed over saidopening in said engine wall, a throttle shaft journaled in saidcarburetor body and closely spaced from said one end of said mixtureconduit, a throttle valve fixed to said shaft for movement therewith andpositioned across said mixture conduit, said body having a fuelreservoir and a fuel passage connecting said fuel reservoir to saidmixture conduit to form an idle system for said carburetor for low speedengine operation, means for rendering said carburetor idle systeminoperative, said last means including a gas passage extending from saidfuel passage through said carburetor body portion to connect with saidopening in said engine wall, and a shim adapted to be positioned betweensaid body portion and said wall opening to close said gas passage tosaid idle system to prevent corrosion of said carburetor by exhaustgases at said opening.

l0. A carburetor for an internal combustion engine having an opening inan outer wall thereof and a conduit for conducting exhaust gases to saidopening, said carburetor comprising a body having a mixture conduittherethrough, said body having a mounting flange at one end of saidmixture conduit for mounting said carburetor body with a portion of saidbody superimposed over said opening in said engine wall, a throttleshaft journaled in said carburetor body and closely spaced from said oneend of said mixture conduit, a throttle valve fixed to said shaft andpositioned across said mixture conduit for movement from a closed to anopen position, said body having a fuel reservoir and a fuel passageconnecting said fuel reservoir to said mixture conduit downstream of theclosed position of said throttle to form an idle system for saidcarburetor for low speed engine operation, and means to preventcorrosion of said carburetor by engine exhaust gas, said last meansincluding a gas passage extending from said fuel passage through saidcarburetor body portion to connect with said opening in said engine walland a shim adapted to be positioned between said body portion and saidwall opening to close said gas passage to said idle system and toseparate said carburetor portion from said engine body opening toprevent corrosion of said carburetor by exhaust gases at said opening.

11. A carburetor for an internal combustion engine having an opening inan outer wall thereof and a conduit for conducting exhaust gases to saidopening, said carburetor comprising a body having a mixture conduittherethrough, said body having means at one end of said mixture conduitfor mounting said carburetor body with an outer surface of said bodysuperimposed over said opening in said engine wall, a throttle shaftjournaled in said carburetor body and closely spaced from said outerbody surface, a throttle valve xed to said shaft and positioned acrosssaid mixture conduit for movement from a closed to an open position,said body having a fuel reservoir and fuel and air passages connectingsaid fuel reservoir to said mixture conduit downstream of the closedposition of said throttle to form an idle system for said carburetor forlow speed engine operation, and means to prevent corrosion of saidthrottle shaft by engine exhaust gas, said last means including a gaspassage extending from said idle system through said carburetor bodyportion to said outer body surface to conduit exhaust gas passingthrough said opening in said engine wall into said idle system and ashim adapted to be positioned between said body surface and said wallopening to close said gas passage to said idle system and to preventcorrosion of said carburetor surface by exhaust gases through saidopening.

12. A carburetor for an internal combustion engine having an opening inan outer wall thereof and a conduit for conducting gases from theexhaust system of said engine to said opening, said carburetorcomprising a body having a mixture conduit therethrough, means formounting salid carburetor body with a body portion adjacent to one endof said mixture conduit superimposed over said opening in said enginewall, a throttle shaft journaled in said carburetor body and closelyspaced from said one end of said mixture conduit, a throttle valve iixedto said shaft for movement therewith and positioned across said mixtureconduit, said body having a fuel reservoir and a fuel passage connectingsaid fuel reservoir to said mixture conduit to form an idle system forsaid carburetor for low speed engine operation, and means to preventcorrosion of said throttle shaft, said last means including a gasconduit extending from said idle system and adapted to be connected tothe exhaust system of said engine and a shim adapted to be positionedbetween said body portion and said wall opening to prevent corrosion ofsaid 7 t carburetor by exhaust gases at said opening, said shim forminga closure for said gas conduit.

13. In combination with an internal combustion engine including anintake manifold for conducting fuel into the engine and an exhaustmanifold for discharge of burnt gases, a carburetor supplying fuel tothe intake manifold including a fuel reservoir and a wall defining aportion of the fuel mixture conduit, means connecting the mixtureconduit to the intake manifold, and idle passage subject to vacuum inthe intake manifold for conducting fuel from the fuel reservoir to themixture conduit for low speed operation of the engine, a throttle valvemounted on a throttle shaft journaled in the mixture conduit portion ofthe carburetor, a conduit means for conducting burnt gases from theexhaust manifold against said portion of the carburetor mixture conduitin the area of the throttle shaft for heating the mixture conduit andthe fuel mixture passing therethrough, a spoilage passage formed in saidwall and opening at one end into said idle system and at the other endcommunicating with the conduit conducting the burnt gases from theexhaust manifold, and a removable heat conducting plate positioned inabutting relation to said portion of the mixture conduit Wall exposed tothe burnt gases for protecting said Wall portion against corrosion fromsaid burnt gases, said heat conducting plate including a portionnormally closing said spoilage passage, whereby removal of the platewill open the idle system to the burnt gas conduit and disable the idlesystem.

References Cited in the le of this patent UNITED STATES PATENTS2,060,498 Gobb Nov. 10, 1936 2,269,706 Brown Ian. 13, 1942 2,684,058Boyce July 20, 1954

1. IN A COMBINATION, AN INTERNAL COMBUSTION ENGINE HAVING AN INTAKEMANIFOLD AND AN EXHAUST SYSTEM, A CARBURETOR MOUNTED ON SAID INTAKEMANIFOLD, SAID INTAKE MANIFOLD HAVING AN EXHAUST GAS PASSAGE ADJACENT TOA PORTION OF SAID CARBURETOR AND CONNECTED TO SAID EXHAUST SYSTEM TOCONVEY HOT EXHAUST GASES TO SAID CARBURETOR PORTION, SAID CARBURETORHAVING AN IDLE SYSTEM CONNECTED TO SAID INTAKE MANIFOLD, A THINCORROSION RESISTANT HEAT CONDUCTIVE SHIM LOCATED BETWEEN SAID CARBURETORPORTION AND SAID INTAKE MANIFOLD AND EXPOSED TO SAID EXHAUST GAS PASSAGETO PROTECT SAID CARBURETOR FROM DAMAGE BY EXHAUST GAS CORROSION, MEANSFOR SPOILING SAID IDLE SYSTEM TO PREVENT SAID ENGINE AT IDLE FROMOPERATING AT LOW SPEEDS IF SAID SHIM IS NOT LOCATED BETWEEN THECARBURETOR AND THE INTAKE MANIFOLD.